Hydraulic slack adjuster



Sept. 10, 1929. L. w. SHUTTS HYDRAULIC SLACK ADJUSTER Filed April 21,1927 gwvmto a r -13y? 5611/7 Fin Patented Sept. 10, 1929.

UNITED STATES PATENT OFFICE.

LEROY W. SHUTTS, OF DETROIT,

MICHIGAN, ASSIGNOR TO GENERAL MOTORS RE- HYDRAUIIC SLACK ADJUSTER.

Application filed April 21, 1927. Serial No. 185,609.

This invention relates to hydraulic mechanism in which motion istransmitted from one member to another through an intervening body offluid and is particularly concerned with a novel arrangement forreplenishing the body of fluid to insure that it is at all-timesmaintained at the proper volume for successful operation. This isaccomplished in a manner similar to that disclosed and claimed in theapplication of George E. A. Hallett, Serial N 0. 186,447 filed April 25,1927, in that the tappet is formed in two parts with an hydraulicchamber between them and that chamber is connected with a supplyreservoir by means of a passage provided with a non-return valve. springis provided tending to separate the members, which may be in the form ofa cylinder and piston, and when the parts contract upon cooling or whenair finds 80 its way into the chamber a pumping action takes place whichdraws oil into the chamber from the reservoir. This action may beaccelerated by supplying oil to the chamher under pressure. According tomy invention the supply form of a housing surrounding the cam shaft andfilled with oil in which the shaft is submerged. By this arrangement notonly is the impact of the cam and tappet cushno ioned by the interposedoil but the sound is muflied so as to be almost inaudible. The oil inthe reservoir may be under pressure or not, as preferred.

I have likewise preferably provided a vent for the removal of air fromthe hydraulic chamber. This may be merely a fixed vent, in which casethe clearance between the cylinder and piston will suflice, or it maytake the form of a thermostatically controlled vent such as thatdisclosed and claimed in the application of John O. Ahnen, Serial No.241,949, filed Dec. 22, 1927. 7

In the drawings, Figure 1 is a vertical section showing my inventionembodied in the valve gear of an internal combustion engine.

Figure 2 is a viewtaken on line 22 of Figure 1.

Figure 3 is a section corresponding to Figure 1 but showing a modifiedform of tappet.

Reference character 6 indicates a portion of pressure provided byreservoir takes the the crankcase of an internal combustion engineprovided with the usual cam shaft 8 for operating the tappet indicatedgenerally by the reference character 10. The tappet, in turn, operatesthe valve' 12. Thecrankcase 6. is formed to provide a recess or trough14 which is completed by the cover 16 bolted to the crankcase. The cover16 is formed to provide a guide 18 in which the tappet reciprocates. Thetrough 14; may extend the length of the engine and may besupplied withoil from the crankcase thru the conduit 20 under the usual oil pump, notshown. The chamber may be provided with a pressure relief valve, notshown, to prevent the building up of excessive pressures in the trough,the discharged oil being re-v turned to the crankcase.

With the described construction, it is apparent that the cam shaft willat all times be submerged in oil so that the impact between the cams andtappets will be cushioned while the little noise still remaining will bemuffled, As air may at times enter the chamber and result in a reductionin the quantity of oil to an amount less than desired, I provide a screwplug 22 in the upper portion of the trough which, when removed, permitsthe escape of air. If desired, a permanently open vent may be used inplace of the screw plug, or some form of automatic vent may be employed,such, for instance, as that used in my improved tappet.

The tappet 10 consists of a cylinder 24 in which is fitted a similarcylindrical member 26. At its lower end the member'24 is provided with atransverse bore 28. The member'26 is provided with a bore communicatingwith the bore 28 and leading to the interior of the cylinder 26. Thebore 30 is con trolled by a spring-pressed check valve 32. Except forconvemence in manufacture, the part 26 might be made integral with thepart 24.

In the upper portion of the member 24 is slidably fitted the piston orplunger 34, the upper end of which engages the stem of the valve. Aspring 36 tends to separate the cylinder and piston.

The head of the piston 34 is provided with a 100 resist wearthanaluminum.

port 38 for the discharge of air from the iydraulic chamber 40 betweenthe cylinder and piston. A port 42 in the upper portion of the member 34permits the escape of the air.

While the port 38 may take the form of a small fixed vent, it ispreferably thermostatically controlled. This I have accomplished in themanner described 'and claimed in the application of John O. Almen,previously referred to. Thus, 44 indicates an aluminum rod fixed in theupper end of the piston 34, the rod carrying at its lower end a valvepart 46 which may be of metal better adapted to The operation of thisvalve, as well as the tappet mechanism, will nowbe described.

I previously explained how the noise caused by the impact of the cam andthe tappet is reduced and mutlled. However, it is well known that owingto the contraction and expansion of the valve parts during operation ofthe engine, clearance develops which may cause noise at the point ofengagement of the valve stem and tappet, as well as between the valveand its seat. To reduce this noise to a minimum, it is necessary toprovide what amounts to a tappet of a size varying in accordance withthe state of contraction or expansion of the parts. This is accomplishedy the described construction in the following manner: If it be assumedthat the engine has just been assembled and that there is no oilcontained in an of the'parts, there would be lost motion or c earance inthe operation of the tappet which would equal the space between theshoulder 50 on the plunger 34 and shoulder 48 on member 26. However, thetappet would operate purely mechanically with that amount of lash. Theoperation would con sequently be very noisy during this period. However,as the engine oil pump fil ed the oil trough 14'through the line 20 towhere the oil level reached the opening 28 in the lower end of thetappet 10, the pumping action then within the tappet itself would causeoil to pass through the valve 32 into the hydraulic chamber 40. In thismanner, oil will thus be admitted to the chamber until the latter isdistended to an extent to take up all clearance. On the subsequentgear,there will be a slight leakage past the thermostatic valve, theescaping oil being replaced from the reservoir in the manner described.If afixed vent were used in place of the thermostatic vent, it isapparent that there would be excessive leakage of oil thru the port 38when the engine is hot and the oil thin. With the thermostatic valve,upon the engine becoming heated the aluminum rod 44 expands at thegreater rate than the steel cylinder 34 so that the clearance. betweenthe member 46 and'its seat is reduced and the "flow is correspondinglydiminished.

operation of the.

Upon the expansion-of the valve stem and parts of the tappet due toheating, the excess oil is forced out of the chamber 40 thru the ort 38until equilibrium of oil flow is again established with the overalllength of the tappet reduced to allow for the expansion.

I have described the trough 14 as filled with oil under pressure.However, if preferred, no pressure need be employed, the pumping actionof the tappet being sufficient to maintain the chamber 40 filled withoil without the aid of the pressure of the oil in the trough.

The form shown in Figure 3 is identical with the form just describedexcept that the clearance indicated at 50 between the plunger 34 and themember 10 is relied upon to permit the escape of air from the chamber40. The plunger 34 is provided with a conical extension 52 serving tohold the spring 40 in position.

I claim 1. The combination of an engine having a cam shaft, a housingfor said cam shaft containing oil in which said shaft is submerged, anoperating member projecting into said housing and actuated by said camshaft, an operated member, a body of oil between said members and thruwhich motion is transmitted between them, and means for replen ishingsaid body from the supply in said housmg.

2. In the combination as defined in claim 1, said means comprising apassage provided with a non-return valve leading oil from said housingto said body.

3. In the combination as defined in claim 1, and means tending toseparate said members to produce pumping action.

4. In the combination as defined in claim 1, said housing being providedwith an air vent at its highest portion.

5. The combination of an engine having a cam shaft, a housing for saidcam shaft, a reciprocating member projecting into said housing forengagement by said cam shaft, a second reciprocating member interfittingwith said first-named member, said members being arranged to provide anhydraulic chamber between them, a passage leading from said housing tosaid chamber, a non-return valve in said passage, and means a body ofoil under pressure in said housing.

6. The combination of an engine having a reservoir of oil underpressure, a cam shaft operating in said reservoir, a multi-part valvetappet in engagement with said cam shaft, hydraulic slack adjustingmechanism associated with said tappet and including a body of fluidinterposed between the parts of the tappet and serving to transmitmotion from one part to the other and means for supplying oil from saidreservoir to said mechanism;

7. The combination of an engine having a reservoir for oil underpressure, a cam shaft operating in said reservoir, a valve tappet in formaintaining engagement with said cam shaft comprising a cylinder, apiston in the cylinder, a body of oil interposed between the piston andcylinder and serving to transmit motion from one to the other and apassage leadin from said cylinder to said reservoir for a mitting oilfrom said reservoir to the space between said v gyliider and piston toreplenish the body of m 8. In the combination as defined in claim 7,

and a non-return valve in said passage.

9. In the combination as defined in claim 7 and a non-return valve insaid passage and means for permitting the escape of air from said space.

10. The combination of an engine having a cam shaft, a housing for saidcam shaft con taining oil in which said shaft is submerged,

a tappet operated by said cam shaft, said tappet being in the form of acylinder, a piston in the cylinder, said piston being supported by abody of oil in said cylinder, a spring tending to separate said pistonand cylinder, and a passage'provided with a non-return valve forconducting oil from said housing to said body to replenish the latter.

11. In the combination as defined in claim 10, said cylinder and pistonbeing provided with co-operating stops to effect emergency mechanicaloperation in the event of failure of said oil supply.

12. :In the combination as defined in claim 10, and means for applyingpressure to the oil in said housing. 13. The combination of an enginehaving a cam shaft, a housing for said cam shaft containing oil in whichsaid shaft'is submerged, an operating member projecting into saidhousing and actuated by said cam shaft, an 40 operated member, a body ofoil between said members and thru which motion is transmitted betweenthem, and means for rendering said body of fluid self-adjusting to takecare of expansion and contraction of the parts upon heating and cooling,said means comprising passages through which the body of fluid may bereplenished from the supply in the housing. In testimony whereof I afiixmy signature. LEROY W. SHUTTS.

